Don't miss Great American Quilt Factory on Hampden and Yosemite, Harriet's Treadle Arts on 44th between Wadsworth and Sheridan, The Creative Needle on Broadway & West Ridge Road (just south of Arapahoe right near Joann's), Holly's Quilt Cabin on Holly and County Line, High Prairie Quilts in Parker ... there are a bunch more that are not near me that are great too! Support your local quilt shop!
If you happen to be in town on the third Monday of the month you could catch a meeting of Front Range Contemporary Quilters or if you're here on the 2nd Thursday of the month, Arapahoe County Quilters. I'm sure there are a bunch of other guilds but I don't know all the schedules.
Also, if you go out to Golden on your way up I-70, stop at CK Media - they always have an awsome (and free) exhibit. Also, take in the Quilt Museum in Golden. They have excellent exhibits (oh and they are also across the street from a quilt shop). And, of course, we have a world class art museum in Denver.
Oh, also on your way up I-70 there is an AWESOME bead shop in Idaho Springs.
Enjoy your trip.